The quest for oceanic sediments within the Ancient Martian sedimentary record

Introduction

The Martian missions have gradually revealed that Mars abounds with evidence of a full ancient hydrological system favorable to life emergence. If so, there are every reason to believe that Mars has hosted a hemispheric ocean covering the northern lowlands. This hypothesis is as old as Mars exploration but has been repeatedly challenged over the past two decades. The case of the primitive Martian ocean remains one of the planet’s most controversial and unsolved issues.

Recent Discoveries

Recent discoveries are re-opening this question, mainly highlighting that the main oceanic activity may be older than we thought. Related deposits are partly exhumed, and two rovers—Mars2020/NASA, which arrived in 2021, and ExoMars/ESA-Roskosmos, to be launched in 2022—have landing sites in the oldest terrains never explored on Mars. These sites display sediments possibly linked with an ocean system.

Requirements for Resolution

To wind up the debate, the identification of ancient deposits of the same age, same composition, with a global distribution in agreement with a possible ocean level is required. However, such clues are small-scale exposures solved only by high-resolution orbital data sets (>10 To of data) or by in situ exploration, preventing a forward link to the global context.

Oceanid Proposal

Oceanid proposes to face this challenge by investigating at different scales:

1. Global
2. Mesoscale
3. Microscale

This will be achieved using complementary datasets (orbital, in situ, and experimental data). Oceanid will also rely on innovative methodology of orbital data mining, including:

• Geological object recognition by artificial intelligence
• Erosion/deposition evolution models
• Clustering from multi-type data

Objectives

Oceanid's objectives are to:

• Describe the early Martian sedimentary record accumulated below possible global ocean levels
• Establish a fine-scale chronology of primitive events
• Contextualize Mars2020 and ExoMars missions within the global ancient hydrological system
• Correlate the oceanic context, the transient water cycle, and the mineralogy observed both from orbit and in situ.